I’m wondering if it is possible to do the following when new record is submitted:
If one column (Assigned To) has a value then put current date in Assigned Date
and ALSO in the same record
if a second column (Completed By) has a value then put the current date in Completed Date.
So I have two conditions that need to be looked at and responded to.
It’s possible, but it’s a bit tedious. If the newly submitted record is from a form, then create an “On Submit” custom action>
If Assigned to is not empty AND Completed by is empty > set column Assigned Date > current date and time
else if Assigned to is not empty AND Completed by is not empty > set column Assigned Date > current date and time & set column Completed Date > current date and time
else if Assigned to is empty AND Completed by is not empty > set column Completed Date > current date and time
This is a use case where a Custom Form would make it a bit easier. You could prepare the date values prior to the form being submitted and then add the lot in one go. Although, there is extra work involved in creating a custom form, so maybe that offsets the effort saved with the action logic 
Thank you, Robert! You’re right, not pretty, but brilliant, that will work.
Darren, thanks for the reply. I’m not quite sure how that works. I am a newbie so not real clear on the custom forms. I just did the “Show Form Screen” to add a new row.
I wouldn’t worry about it, my response was slightly tongue in cheek 
The option that Bob gave you is perfectly fine 